CN111792647A - Method for smelting silicon wafer cutting waste under micro-negative pressure - Google Patents
Method for smelting silicon wafer cutting waste under micro-negative pressure Download PDFInfo
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- CN111792647A CN111792647A CN202010705503.4A CN202010705503A CN111792647A CN 111792647 A CN111792647 A CN 111792647A CN 202010705503 A CN202010705503 A CN 202010705503A CN 111792647 A CN111792647 A CN 111792647A
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 117
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 103
- 239000010703 silicon Substances 0.000 title claims abstract description 103
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
- C01B33/037—Purification
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- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Silicon Compounds (AREA)
Abstract
The invention relates to a method for smelting silicon slice cutting waste under micro-negative pressure, and belongs to the technical field of silicon recycling by pyrogenic smelting of silicon slice cutting waste. Aiming at the problems that silicon powder is easy to oxidize in the smelting process and impurity removal efficiency is low in the smelting process due to the existence of moisture in the process of smelting and recovering silicon by a pyrogenic process, the micro-negative pressure device is moved to the position right above a smelting furnace mouth, and a vacuum device of the micro-negative pressure device is started to carry out micro-negative pressure smelting on the silicon chip cutting waste, so that the oxidation loss of superfine silicon powder in the smelting process is avoided, volatile impurities in the silicon are removed, and the silicon melt is synchronously refined. The micro-negative pressure environment is created above the silicon melt, so that the escape of smoke in the silicon melting process can be avoided, and the environmental influence is reduced. The method has the advantages of simple equipment requirement, easy operation, environmental protection and suitability for large-scale industrial production.
Description
Technical Field
The invention relates to a method for smelting silicon slice cutting waste under micro-negative pressure, and belongs to the technical field of silicon recycling by pyrogenic smelting of silicon slice cutting waste.
Background
Due to the use of additives and other auxiliary materials and the oxidation under working conditions of cutting/storage, transportation and the like in the silicon wafer cutting process, the silicon wafer cutting waste has high content of aluminum and calcium impurities and high surface oxidation degree of ultrafine silicon particles to generate a silicon dioxide layer, so that the removal of the aluminum and calcium impurities is ensured in the process of preparing high-purity silicon by regenerating and purifying the silicon wafer cutting waste, and the silicon particles are prevented from contacting with oxygen to the maximum extent in the smelting process, so that the oxidation loss of silicon is reduced. In the prior art, the silicon wafer cutting waste is directly smelted in a furnace and added with a slagging constituent for auxiliary smelting, different steps are respectively adopted to separate a silicon dioxide layer and remove aluminum and calcium impurities, the process is long, the process is complex, the participation of oxygen in the smelting process is difficult to accurately control, the secondary oxidation of the superfine silicon powder is aggravated, and the removal rate of the impurities is low.
Disclosure of Invention
In order to realize the high-efficiency recovery and high-valued recycling of silicon in the silicon wafer cutting waste, simultaneously realize the reduction of the participation of oxygen, the improvement of the removal of impurities and the guarantee of the recovery rate and the purity of silicon in the smelting process, the invention provides a method for smelting the silicon wafer cutting waste under the micro-negative pressure, namely, a micro negative pressure device is arranged at the upper part of silicon melting main body equipment, namely a micro negative pressure state is built at a gas-liquid interface of high-temperature silicon melt in the melting process, can reduce the participation degree of air or oxygen as much as possible in the smelting process, eliminates the direct contact of oxygen and high-temperature silicon melt, avoids the oxidation loss of the superfine silicon powder under the high-temperature condition, meanwhile, a negative pressure state is generated at a gas-liquid interface in the smelting process through a micro negative pressure environment, so that volatile impurities in the high-temperature silicon melt are promoted to be volatilized and removed in the smelting process, and the purpose of synchronously refining and purifying the silicon liquid in the smelting process of the silicon wafer cutting waste is achieved.
A method for smelting silicon wafer cutting waste under micro-negative pressure comprises the following specific steps:
and moving the micro negative pressure device to be right above a smelting furnace opening, and starting a vacuum device of the micro negative pressure device to enable the silicon wafer cutting waste to be subjected to micro negative pressure smelting and synchronous refining so as to avoid oxidation loss of the superfine silicon powder in the smelting process and remove volatile impurities in the silicon melt.
The smelting comprises air blowing smelting, slagging smelting or air blowing-slagging composite smelting.
Further, the oxygen introducing mode can specifically adopt bottom blowing, top blowing, side blowing or eccentric blowing and the like aiming at different furnace types; the slag agent can be one or more of oxide, fluoride and fluoroaluminate; the gas can be air, wet oxygen, industrial oxygen or oxygen-enriched air, and can also be mixed gas containing argon, nitrogen and water; blowing in gas not only can play the effect of edulcoration, can also acutely stir silicon melt simultaneously, thereby make the gas-liquid interface of furnace mouth department constantly renew when guaranteeing impurity abundant and edulcoration agent reaction and more do benefit to volatile impurity and volatilize and get rid of.
The micro-negative pressure device comprises a smoke collecting hood, a flue, a vacuum unit and a dust collecting device which are sequentially connected, wherein the smoke collecting hood is arranged right above a furnace mouth of the smelting device, and the smoke collecting hood is hermetically connected with the furnace mouth of the smelting device to form a closed cavity.
Further, the outer wall of the hood may be connected to an overhead crane suspension or lift-swivel member system. The lifting-rotating component comprises a controller, a driving servo motor I, a driving servo motor II, a transmission shaft I, a transmission shaft II and a clamping connecting rod, wherein one end of the clamping connecting rod is fixedly connected with the outer wall of the smoke collecting hood, the other end of the clamping connecting rod is fixedly connected with the top end of the transmission shaft I, the bottom end of the transmission shaft I is connected with the top end of the transmission shaft II through a ball bearing or a needle bearing, the transmission shaft I can rotate at the top end of the transmission shaft II, the bottom end of the transmission shaft II is fixedly connected with an output shaft of the driving servo motor II, the driving servo motor II is a stepping reciprocating motor, the driving servo motor I is fixedly arranged on the transmission shaft II through a supporting rod, a gear I is arranged on the output shaft of the driving servo motor I, a gear II is sleeved on; the driving servo motor I and the driving servo motor II are respectively and electrically connected with the controller.
Furthermore, a fire-resistant layer and a cooling water jacket are arranged on the outer wall of the smoke collecting hood;
the top opening of the smelting device can be used for introducing gas from the top, adding a slagging agent and pouring slag and silicon liquid, smoke and dust fume generated in the smelting process is generated at a gas-liquid interface and collected in a fume collecting hood under the action of micro negative pressure, the area of a fume collecting hood opening can cover the whole top opening of the smelting device, and a lifting-rotating component of the fume collecting hood can be adjusted in height according to different smelting periods, for example, the fume collecting hood can be properly lifted in the ventilation process and the slagging agent, and the fume collecting hood can be lifted to a specific height in the silicon liquid adding or discharging process; the fire-resistant layer of the smoke collecting hood can ensure that the smoke collecting hood can bear different smelting temperatures;
the smelting device can be a ladle furnace, a tundish, a graphite crucible or other special smelting equipment;
the heating mode of the smelting device comprises but is not limited to: resistance heating, induction heating, plasma, arc furnace heating, self-heating of reaction production or heat capacity of silicon melt, etc.;
the fume collecting hood can be in the shape of a round bottom, a conical shape, a tetrahedral frustum and the like, and the specific size and the cross section shape can be determined according to the geometric shape and the size of a top opening of a specific smelting device so as to ensure the complete connection between the fume collecting hood and a furnace opening, thereby avoiding the escape, the overflow, the leakage and the like of furnace gas and ensuring the micro negative pressure environment in the fume collecting hood;
the smoke collecting hood can be made of a stainless steel shell layer, a steel sleeve and the like, and the outer wall of the smoke collecting hood is lined with a fire-resistant layer and a cooling water jacket, so that the rigidity, the strength and the high temperature resistance of the smoke collecting hood are ensured, and the pollution of an external pollution source to the silicon melt is avoided;
the vacuum equipment of the vacuum device is a one-stage or multi-stage combined vacuum pump, and the vacuum pump is a rough pumping mechanical pump or a molecular pump; the vacuum system can be determined according to the content and the type of impurities in silicon wafer cutting waste materials with different sources or batches or silicon wafer cutting waste material molten silicon melt, for example, the silicon wafer cutting waste materials with high volatile impurities can adopt a multi-stage vacuum pump to keep the furnace mouth with relatively high vacuum degree, so that the deep removal of a large amount of volatile impurities is ensured, and the smelting period can be effectively shortened.
The dust collecting system can be a cloth bag, cyclone, gravity or electrostatic dust collecting equipment and can simultaneously collect micro silicon powder, silicon powder and the like carried in smoke dust in the smelting process.
The invention has the beneficial effects that:
(1) according to the method, a micro negative pressure state is established at the upper part of silicon melting main body equipment, namely a gas-liquid interface of high-temperature silicon melt in the melting process of silicon wafer cutting waste through the micro negative pressure device, so that contact oxidation of superfine silicon powder and oxygen under a high-temperature condition is avoided, the oxidation loss of the superfine silicon powder is reduced, the recovery rate of silicon is improved, and the production yield is improved;
(2) according to the method, a micro negative pressure state is established at the upper part of the silicon melting main body equipment through the micro negative pressure device, so that the volatile impurities in the melt are volatilized and removed in the melting process, the volatile impurities in the melt are deeply removed, and the purity of the industrial silicon product is improved;
(3) according to the method, a micro negative pressure state is built at the upper part of the silicon melting main body equipment through the micro negative pressure device, so that the purpose of synchronously refining and purifying silicon melt in the silicon wafer cutting waste material melting process is realized, the procedures of conventional industrial silicon furnace external refining and purifying are reduced, the high-purity industrial silicon smelting process is shortened, the unit production energy consumption is saved, and the method belongs to a new clean production technology;
(4) according to the method, a micro negative pressure state is built at the upper part of the silicon melting main body equipment through the micro negative pressure device, so that the oxidation contact of superfine silicon powder and air or oxygen in the high-temperature melting process is reduced to the maximum extent, the requirement on the selectivity of raw materials in the melting process is reduced, the raw materials are more applicable to silicon wafer cutting waste raw materials with high oxygen content and high impurity content, the problems that the raw materials with high oxygen content and high impurity content are difficult to process and insufficient in utilization rate are solved, and the pollution influence on the environment in the process of accumulating a large amount of raw materials difficult to process is reduced;
(5) the method is a low-cost and high-efficiency auxiliary impurity removal method for the silicon wafer cutting waste, and has the advantages of simple equipment, easiness in operation, suitability for large-scale industrial production and the like.
Drawings
FIG. 1 is a schematic view of a micro-negative pressure device and a smelting device;
fig. 2 is a schematic diagram of the lift-rotate system connection.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but the scope of the present invention is not limited to the description.
The invention relates to a schematic diagram of a micro-negative pressure device and a smelting device, which is shown in figure 1, wherein the micro-negative pressure device comprises a smoke collecting hood, a flue, a vacuum unit and a dust collecting device which are sequentially connected, the smoke collecting hood is arranged right above a furnace mouth of the smelting device, and the smoke collecting hood is hermetically connected with the furnace mouth of the smelting device to form a closed cavity; the outer wall of the fume collecting hood is connected with a lifting-rotating component which comprises a controller, a driving servo motor I and a driving servo motor II, the device comprises a transmission shaft I, a transmission shaft II and a clamping connecting rod, wherein one end of the clamping connecting rod is fixedly connected with the outer wall of the smoke collecting hood, the other end of the clamping connecting rod is fixedly connected with the top end of the transmission shaft I, the bottom end of the transmission shaft I is connected with the top end of the transmission shaft II through a ball bearing or a needle bearing, the transmission shaft I can rotate at the top end of the transmission shaft II, the bottom end of the transmission shaft II is fixedly connected with an output shaft of a driving servo motor II, the driving servo motor II is a stepping reciprocating motor, the driving servo motor I is fixedly arranged on the transmission shaft II through a supporting rod, a gear I is arranged on the output shaft of the driving servo motor I, a gear II is; the driving servo motor I and the driving servo motor II are respectively and electrically connected with the controller; the outer wall of the smoke collecting hood is provided with a fire-resistant layer and a cooling water jacket; the top opening of the smelting device can be used for introducing gas from the top, adding a slagging agent and pouring slag and silicon liquid, smoke and dust fume generated in the smelting process is generated at a gas-liquid interface and collected in the fume collecting hood under the action of micro negative pressure, the area of a fume collecting hood opening can cover the whole top opening of the smelting device, and a lifting-rotating component of the fume collecting hood can be adjusted in height according to different smelting periods, for example, the fume collecting hood can be properly lifted in the ventilation process and the slagging agent, and the fume collecting hood can be lifted to a specific height in the silicon liquid adding or discharging process; the fire-resistant layer of the smoke collecting hood can ensure that the smoke collecting hood can bear different smelting temperatures; the smoke collecting hood can be in the shape of a round bottom, a conical shape, a tetrahedral frustum and the like, and the specific size and the cross section shape can be determined according to the geometrical shape and the size of a top opening of a specific smelting device so as to ensure the complete connection between the smoke collecting hood and a furnace opening, thereby avoiding the escape, the overflow, the leakage and the like of furnace gas and ensuring the micro negative pressure environment in the smoke collecting hood; the smoke collecting hood can be made of a stainless steel shell layer, a steel sleeve and the like, and the outer wall of the smoke collecting hood is lined with a fire-resistant layer and a cooling water jacket, so that the rigidity, the strength and the high temperature resistance of the smoke collecting hood are ensured, and the pollution of an external pollution source to the silicon melt is avoided; the vacuum equipment of the vacuum device is a one-stage or multi-stage combined vacuum pump, and the vacuum pump is a rough pumping mechanical pump or a molecular pump; the vacuum system can be determined according to the content and the type of impurities in silicon melts from different sources or in different batches, for example, the silicon melt containing higher volatile impurities can adopt a multi-stage vacuum pump to keep the furnace mouth at a relatively higher vacuum degree, so that the deep removal of a large amount of volatile impurities is ensured, and the smelting period can be effectively shortened; the dust collecting system can be a cloth bag, cyclone, gravity or electrostatic dust collecting equipment and can simultaneously collect micro silicon powder, silicon powder and the like carried in smoke dust in the smelting process.
Example 1: a method for smelting silicon wafer cutting waste under micro-negative pressure comprises the following specific steps:
(1) induction melting is carried out on silicon chip cutting waste materials in a certain place in Yunnan, so that bulk powder is melted into high-temperature silicon liquid; in percentage by mass, the impurity content in the silicon chip cutting waste is 6000ppm of Al and 3000ppm of Ca;
(2) in order to further reduce Al and Ca, in the step (1), carrying out micro-negative pressure smelting, moving a smoke collecting hood of a micro-negative pressure device to be right above a furnace mouth of a smelting device (an induction furnace) through a lifting-rotating component so that the smoke collecting hood mouth can cover the furnace mouth, starting a vacuum device (a two-stage combined mechanical vacuum pump) of the micro-negative pressure device to carry out micro-negative pressure smelting and synchronous refining on silicon wafer cutting waste so as to avoid oxidation loss of the superfine silicon powder in the smelting process and remove volatile impurities in silicon melt, wherein the pressure of the furnace mouth is about 0.1 atmosphere, and the micro-negative pressure smelting lasts for 10min after the ventilation is finished;
(3) closing the micro negative pressure device after the micro negative pressure smelting is finished, moving the micro negative pressure device to an initial position, and carrying out external casting on the impurity-removed silicon melt smelted in the step (2) under the micro negative pressure to obtain an industrial silicon product;
the content of impurities in the industrial silicon product of the embodiment is Al <800ppm and Ca <600ppm in percentage by mass.
Example 2: a method for smelting silicon wafer cutting waste under micro-negative pressure comprises the following specific steps:
(1) induction melting is carried out on silicon chip cutting waste materials in a certain place in Yunnan, so that bulk powder is melted into high-temperature silicon liquid; the impurity content of the silicon chip cutting waste is 11000ppm and the Ca content is 3000ppm in percentage by mass;
(2) in order to further reduce Al and Ca, slagging and smelting the high-temperature silicon liquid obtained by induction smelting in the step (1); wherein the slagging agent is CaO, and the addition amount of the CaO is 2 kg/ton based on the mass of the silicon wafer cutting waste; adding a slagging agent CaO, and introducing industrial compressed nitrogen for about 15 min;
(3) carrying out micro-negative pressure smelting while slagging smelting in the step (2), moving a smoke collecting hood of a micro-negative pressure device to be right above a ladle opening of a smelting device through a lifting-rotating component, enabling the smoke collecting hood opening to cover the ladle opening, starting a vacuum device (two-stage combined mechanical vacuum pump) of the micro-negative pressure device to carry out micro-negative pressure smelting on silicon wafer cutting waste, and carrying out micro-negative pressure smelting and synchronous refining and purification on silicon melt melted by the silicon wafer cutting waste so as to remove volatile impurities in the silicon melt, wherein the pressure of a furnace opening is about 0.1 atmosphere, and the micro-negative pressure smelting lasts for 5-10 min after ventilation is finished;
(4) closing the micro negative pressure device after the micro negative pressure smelting is finished, moving the micro negative pressure device to an initial position, and carrying out external casting on the impurity-removed silicon melt smelted in the step (3) under the micro negative pressure to obtain an industrial silicon product;
the content of impurities in the industrial silicon product of the embodiment is Al <600ppm and Ca <800ppm in percentage by mass.
Example 3: a method for smelting silicon wafer cutting waste under micro-negative pressure comprises the following specific steps:
(1) induction melting is carried out on silicon chip cutting waste materials in a certain place in Yunnan, so that bulk powder is melted into high-temperature silicon liquid; the impurity content of the silicon chip cutting waste is 8000ppm and the Ca content is 500ppm in percentage by mass;
(2) in order to further reduce Al and Ca, the high-temperature silicon liquid obtained by the induction smelting in the step (1) is subjected to blowing slagging composite smelting; wherein the blowing is top blowing, the gas is industrial oxygen, the aeration time is about 10min, the aeration pressure is 1.2-2 atmospheric pressures, and the gas flow rate is 0.2-1m3S; the slagging agent is CaO, and the addition amount of the CaO is 1 kg/ton based on the mass of the silicon wafer cutting waste;
(3) carrying out micro-negative pressure smelting while blowing, slagging and smelting in the step (2), moving a smoke collecting hood of a micro-negative pressure device to be right above a furnace mouth of a smelting device through a lifting-rotating component, enabling the smoke collecting hood mouth to cover the furnace mouth, starting a vacuum device (two-stage combined mechanical vacuum pump) of the micro-negative pressure device to carry out micro-negative pressure smelting on silicon wafer cutting waste, and carrying out micro-negative pressure smelting on silicon melt melted by the silicon wafer cutting waste and synchronous refining and purification to remove volatile impurities in the silicon melt, wherein the pressure of the furnace mouth is about 0.1 atmosphere, and the micro-negative pressure smelting lasts for 5-10 min after ventilation is finished;
(4) closing the micro negative pressure device after the micro negative pressure smelting is finished, moving the micro negative pressure device to an initial position, and carrying out external casting on the impurity-removed silicon melt smelted in the step (3) under the micro negative pressure to obtain an industrial silicon product;
the content of impurities in the industrial silicon product of the embodiment is Al <200ppm and Ca <300ppm in percentage by mass.
Claims (5)
1. A method for smelting silicon wafer cutting waste under micro-negative pressure is characterized by comprising the following specific steps:
and moving the micro negative pressure device to be right above a smelting furnace opening, and starting a vacuum device of the micro negative pressure device to enable the silicon wafer cutting waste to be subjected to micro negative pressure smelting and synchronous refining so as to avoid oxidation loss of the superfine silicon powder in the smelting process and remove volatile impurities in the silicon melt.
2. The silicon wafer cutting waste material micro-negative pressure smelting method according to claim 1, characterized by comprising the following steps: the smelting comprises air blowing smelting, slagging smelting or air blowing-slagging composite smelting.
3. The silicon wafer cutting waste material micro-negative pressure smelting method according to claim 1, characterized by comprising the following steps: the micro-negative pressure device comprises a smoke collecting hood, a flue, a vacuum unit and a dust collecting device which are sequentially connected, wherein the smoke collecting hood is arranged right above a furnace mouth of the smelting device and is hermetically connected with the furnace mouth of the smelting device to form a closed cavity.
4. The silicon wafer cutting waste material micro-negative pressure smelting method according to claim 3, characterized by comprising the following steps: the outer wall of the smoke collecting hood is connected with a crown block suspension or lifting-rotating component system.
5. The silicon wafer cutting waste material micro-negative pressure smelting method according to claim 4, characterized in that: the lifting-rotating component comprises a controller, a driving servo motor I, a driving servo motor II, a transmission shaft I, a transmission shaft II and a clamping connecting rod, one end of the clamping connecting rod is fixedly connected with the outer wall of the smoke collecting hood, the other end of the clamping connecting rod is fixedly connected with the top end of the transmission shaft I, the bottom end of the transmission shaft I is connected with the top end of the transmission shaft II through a ball bearing or a needle bearing, the transmission shaft I can rotate at the top end of the transmission shaft II, the bottom end of the transmission shaft II is fixedly connected with an output shaft of the driving servo motor II, the driving servo motor II is a stepping reciprocating motor, the driving servo motor I is fixedly arranged on the transmission shaft II through a supporting rod, a gear I is arranged on the output shaft of the driving servo motor I, a gear II is sleeved; the driving servo motor I and the driving servo motor II are respectively and electrically connected with the controller.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111646478A (en) * | 2020-07-14 | 2020-09-11 | 昆明理工大学 | Micro-negative pressure external refining method for industrial silicon melt |
| CN112456499A (en) * | 2020-12-11 | 2021-03-09 | 昆明理工大学 | Method for preparing high-purity silicon by using silicon cutting waste |
| CN113023732A (en) * | 2021-03-05 | 2021-06-25 | 昆明理工大学 | Method for preparing high-purity silicon by recovering silicon wafer cutting waste |
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| CN111646478B (en) * | 2020-07-14 | 2022-07-29 | 昆明理工大学 | Micro-negative pressure external refining method for industrial silicon melt |
| CN112456499A (en) * | 2020-12-11 | 2021-03-09 | 昆明理工大学 | Method for preparing high-purity silicon by using silicon cutting waste |
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